A condemned killer in the state of Ohio has been executed by a lethal combination of two drugs never before used in the United States.

Authorities in Ohio used a mix of the sedative midazolam and pain killer hydromorphone Thursday to execute Dennis McGuire, who was sentenced to death for raping and fatally stabbing a young pregnant woman in 1989.

Last year, 39 prisoners were executed by U.S. states. Many were killed by drugs including the barbiturate pentobarbital. The drug is manufactured by European-based companies that stopped sales to U.S. prisons when they realized their product was used for executions.

When it ran out of pentobarbital, Ohio put together its new mix of drugs over the protests of McGuire's lawyers. They said the concoction would cause him agony and terror and result in his death by suffocation.

Witnesses said the 53-year-old died about 15 minutes after receiving the drugs - a period of time said to be unusually lengthy. McGuire appeared to gasp several times before he stopped breathing.